- Volume 14, Issue 2, 1956

Summary: Mutants of Aspergillus niger, Wisconsin strain 72–4, were produced by multiple X-ray and ultraviolet irradiation. The mutants differed from the parent strain culturally and in citric acid production. Comparison between the yields of citric acid from the parent strain and mutants showed significant increases with the latter. In crude sugar media, such as ferrocyanide-treated brown sugar, yields of citric acid equivalent to 80% of the sugar fermented were obtained in aerated culture, whereas only 21% was obtained with the parent strain.

SUMMARY: Heterotrophic bacteria were studied which produced nitrite in the presence of ammonia and in the absence of nitrate. A soil extract medium was prepared which allowed good growth as well as nitrite production in the absence of nitrate. Quantitative data are recorded showing that ammonia decreases as nitrite accumulates when four different cultures are grown in the soil medium. Resting cell studies add further evidence that some heterotrophic bacteria can convert ammonia to nitrite.

A defined medium was prepared containing glucose or sodium acetate as the carbon source and NH4Cl as the nitrogen source. This medium supported growth and nitrite production; however, optimum conditions for growth were not established. Neither growth nor nitrite accumulation was as great in defined media as in soil-extract media. Results from defined media and from resting-cell studies rule out the possibility of any nitrate contamination.

SUMMARY: A complete quantitative amino acid analysis of the free amino acid fraction and the mycelial residue fraction of the mould Aspergillus flavus during different stages of growth has been made by the circular paper chromatographic technique. A qualitative analysis of the amino acid composition of the culture fluid has also been accomplished. The changes of the individual amino acids present in the various fractions on different days of incubation were studied and their implications discussed.

Summary: Certain anaerobic bacteria from human faeces were found to be able to hydrogenate cholesteroli n vitro; some also decreased to a marked degree the total amount of sterols in the incubation mixture. Other organisms did not hydrogenate or decrease the amount of sterols under the conditions chosen; among these were; Clostridium welchii, C. sporogenes, Bacterium bifidum, various streptococci and micrococci, Escherichia coli, Aerobacter aerogenes. A germ-free filtrate from human faeces was inactive. In a series of incubated samples, where the Tschugaeff reaction was applied to the non-saponifiable matter, an orange colour developed, suggestive of the presence of lathosterol.

Summary: Biochemical mutants of Erwinia aroideae displayed a pattern of virulence and avirulence for varieties of radish and turnip similar to the pattern previously reported for different host species. Three types of host response were noted when slices of the fleshy storage organs were inoculated: uniformly resistant, uniformly susceptible, and a variable response in which individuals of a given variety may be resistant or susceptible to a specific mutant. Prototrophic reversions from an avirulent mutant requiring arginine and from an uncharacterized mutant with diminished virulence were as virulent as the parental strain for all varieties of radish and turnip.

Summary: The non-pathogenic beta-haemolytic streptococci from milk, forming Lancefield’s group E, were physiologically defined as Streptococcus infrequens and S. subacidus. They were found to fall into four serological types. Fractionation with ethanol showed that both group- and type-specific fractions of these organisms are of polysaccharide nature which probably accounts for the success in using formamide extracts for the type-precipitin reactions. S. subacidus possesses two type antigens, only one of which is also found in S. infrequens.

Summary: It was found that a mutant strain of Myxococcus virescens, able to grow dispersed in liquid media, oxidized the cytoplasmic lipids and proteins of Escherichia coli. Cell walls and nucleic acids of E. coli were not oxidized, and the acid soluble fraction was only slightly oxidized. It was also observed that the cytoplasmic contents of intact cells of E. coli were not available for oxidation. Glucose and starch were oxidized by the strain of Myxococcus virescens used.

Summary: Biophysical studies of the virus system of vesicular stomatitis passaged in eggs showed that the major part of the infectivity was associated with a component of sedimentation coefficient 625S. A component of sedimentation coefficient 330 S was observed also, and is probably a non-infective product of the disintegration of the 625S component. These components contribute about 35% of the total complement-fixing activity of the virus system. All infective materials were handled in subdued light (Skinner & Bradish, 1954). Electron micrographs of concentrates of the infective fraction revealed rods, of length 175 mμ. and diameter 69 mμ., and almost spherical granules of diameter 65 m. These particles are identified with the 625S and 330S sedimentation components. The remaining 65% of the total complement-fixing activity was associated with two discrete components of sedimentation coefficients about 20S and 6S. The first of these components may contribute up to 0·1% of the total infectivity of the virus system. The structure of the virus system is discussed in relation to the data obtained.

Summary: Suspensions of non-proliferating Escherichia coli produced H2S from thiosulphate in the presence of pyruvate or acetaldehyde. Production of H2S was slight in the presence of α-ketoglutarate and α-ketobutyrate. Organic acids such as malate, fumarate, succinate, lactate, formate and acetate, aldehydes other than acetaldehyde and monohydric alcohols either had no effect or inhibited H2S production from thiosulphate. H2S was not produced from sulphite, bisulphite or sulphate, either in the presence or in the absence of the above-named compounds. Crude cell-free extracts of Escherichia coli produced H2S from thiosulphate in the presence of pyruvate. Experiments with dialysed extracts showed that inorganic phosphate, Mg ions and cocarboxylase were essential for H2S production. Treatment of the extracts with anion exchange resin revealed that in addition, coenzyme A was indispensable for H2S production from thiosulphate. The addition of DPN to extracts dialysed or treated with anion exchange resin did not influence H2S production to a marked degree.

Summary: Apple pectin in a complex organic medium partly protected Escherichia coli strain B from lysis by T2 phage. It was not bactericidal or virucidal. The rate of adsorption of the phage was unaltered, but part of the initially adsorbed phage could be eluted with distilled water at 0°, as the second irreversible step of adsorption was inhibited by pectin. It was shown in one-step growth and single cell burst experiments that phage multiplication was reduced. The release of any formed phage from the host was not affected. The protective effect of the pectin resulted from the failure of some of the phage particles to penetrate into the host cell and from its action in decreasing phage synthesis in those cells where penetration did take place. It is suggested that this non-specific polysaccharide may exert its protective action because of its polymeric electrolyte nature.

Summary: Eight strains of Azotobacter agile and A. vinelandii were studied for their ability to elaborate water soluble compounds with a fluorescence that would characterize each when observed under ultraviolet light of 3600 A. It was found that the material produced by A. agile fluoresced white, whereas that produced by A. vinelandii fluoresced green. Additional studies with iron and molybdenum showed that molybdenum enhanced synthesis of fluorescent material in both species and iron appeared to quench the fluorescence. A pH/fluorescence curve for the fluorescent material of each species showed that, although similarities were evident, sufficient difference existed to permit recognition of each. Analyses of dried cell material revealed a much higher protein content in A. agile than in A. vinelandii, but the amount of one of their amino acids, lysine, was essentially the same, on the basis of protein, for each species.

Summary: An organism able to grow in a simple medium with creatine as the main C and N source was isolated from garden soil and subsequently identified as Pseudomonas ovalis Chester. Organisms harvested from a creatine-containing medium destroyed creatine with the uptake of O2 and the formation of CO2, NH2 and urea. With the exception of urea the quantities of reactants fell short of those required by theory, and only part of the deficiency could be attributed to oxidative assimilation. Optimal conditions for the growth of active organisms and for the destruction of creatine were determined. In these conditions the organisms destroyed, in addition to creatine, only arginine and agmatine from a variety of compounds tested; compounds not attacked included creatinine and glycocyamine. Ability to oxidize creatine was partially lost during repeated washing and storage of the organisms, and was inhibited by p-chloromercuribenzoic acid and fatty acids.

SUMMARY: Creatine is oxidized by suspensions of a strain of Pseudomonas ovalis Chester harvested from media containing creatine as main source of carbon and nitrogen. A possible pathway of degradation of at least part of the creatine is: (a) hydrolysis of creatine to sarcosine and urea, (b) oxidation of sarcosine to glycine and formaldehyde, (c) oxidation of the latter products to CO2 and NH3 with considerable concurrent oxidative assimilation.

Soluble enzyme preparations catalysing stage (a) were obtained by aqueous extraction of either acetone-dried or toluene-treated organisms. The enzyme for stage (b) was present in the insoluble residue from the latter organisms.

SUMMARY: Many aliphatic organic acids, when sprayed on the leaves of bean plants, decreased the numbers of local lesions produced following inoculation with a tobacco necrosis virus. Citric and succinic acids were effective only when applied before or during the period of virus establishment. The inhibitory effect of these acids could be annulled by certain metal nitrates.

SUMMARY: During normal movement most motile bacteria carry a straight tail, which, when the movement slows, stiffens into helical structures commonly called flagella. The helices of many kinds of bacteria were photographed with a sunlight dark-ground microscope, and their wavelengths measured. Mean values and standard deviations were calculated for each strain and then for the species. ‘Biplicity’ (two wavelengths per bacterium, one twice the other) was observed frequently. Each strain appears to have its own constant wavelengths. The wavelength differs in different kinds of bacteria from 0·60 to 5·058μ., the distribution over the various species not revealing a distinct pattern nor any obvious correlation with other characteristics. The wavelength is affected by temperature, pH value, and colloid content of medium. These features, and the effects of drying, make stained preparations useless for measuring.

SUMMARY: Several species of soil actinomycetes arrested the growth of fungi by antibiotic secretions on agar media containing 10 g. glucose/1. On media of lower glucose concentration, the fungi continued to grow in the presence of the actinomycetes, but there was evidence that traces of antibiotic substances were still being formed. In sand moistened with liquid medium containing glucose, S. albidoflavus limited early growth of Fusarium culmorum by antibiotic action and also attacked preformed fungus mycelium directly. The effectiveness of these antagonistic mechanisms was decreased when the glucose concentration was lowered. The fungus and the actinomycete grew together on a variety of natural organic materials, but only when dried grass was used did the actinomycete arrest growth of the fungus at a distance.

SUMMARY: An antibiotic present in culture filtrates of Streptomyces albidoflavus was inactivated by clays and by suspensions and extracts of soils. When this actino-mycete was grown with Fusarium culmorum in a sand + bentonite mixture moistened with nutrient solution, it did not antagonize the fungus by antibiotic secretions. However, suppression of fungus growth was observed even in the presence of bentonite particularly when glucose was present in abundance; this effect was attributed to competition between the organisms for limiting nutrients. The actinomycete also lysed the contents of the fungus mycelium in sand culture but not when bentonite was added. The lytic agent appeared to differ from the antibiotic. Neither antibiotic action nor direct (lytic) attack on the fungus was demonstrated in sterilized soil.

SUMMARY: The effect of various substrates on the oxygen uptake of Mycobacterium smegmatis grown in the presence of glucose and glycerol was investigated; isoniazid had no effect on these oxidations. Three different effects of isoniazid on the metabolism of this organism were demonstrated, (i) Growth of the organism in a minimal medium in the Warburg apparatus was prevented by the addition of isoniazid, the amount required being related to the number of organisms present, their age and their sensitivity to the drug as measured by serial dilution in the test tube, (ii) In confirmation of the report of Zeller, Barsky, Berman & Fouts (1952) it was found that isoniazid inhibited the oxidation of putrescine by M. smegmatis. (iii) Following the work of Gray (1953) the effect of isoniazid on the oxidation of various substrates by M. smegmatis grown in the absence of glucose and glycerol was studied. Isoniazid caused a 30 % inhibition of the oxidation of acetate. The amount of isoniazid required to inhibit the oxidation of putrescine and acetate was the same whether the strain used was sensitive or resistant to isoniazid as measured by growth in the test tube.

In an attempt to discover the mechanism by which isonicotinic acid hydrazide (isoniazid) inhibits the growth of mycobacteria, the effect of isoniazid on their respiration was investigated. Preliminary work involved a study of the oxidative metabolism of the saprophytic organism Mycobacterium smegmatis.

SUMMARY: Isoniazid inhibited the oxidation of acetate in the Warburg apparatus by Mycobacterium tuberculosis B.C.G. and other mycobacteria but not by any of the other organisms tested. This effect was investigated in more detail with B.C.G. Inhibition of acetate oxidation was obtained by isoniazid whatever medium had been used for growth. The amount of isoniazid required for inhibition was related to the number of organisms present and their sensitivity to isoniazid as measured by the usual test-tube method. None of the substances reported to antagonize isoniazid inhibition was effective in annulling inhibition by isoniazid in this acetate oxidation system. The effect of various mixtures of drugs on acetate oxidation was tested. Concentrations of isoniazid and streptomycin which when used singly were insufficient to inhibit acetate oxidation, were inhibitory when used together. Similarly, mixtures of isoniazid + p-aminosalicylic acid (P.A.S.) or terramycin, or of strepto-mycin + P.A.S., at concentrations which were subinhibitory when used singly, were also effective in inhibiting acetate oxidation. It is suggested that the action of drugs or drug mixtures could usefully be investigated by this or similar techniques which have the advantage of largely eliminating the selection of resistant strains.